NCERT Class 7 Science Chapter 2 Nutrition in Animals: Notes, Solutions, Free PDF

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Class 7 Chapter 2 Nutrition in Animals

NCERT Class 7 Science Chapter 2 deals with Nutrition in Animals. Through the notes in this chapter, we have explained all important concepts such as different ways of taking food and the digestive system in human beings, grass-eating animals, and an amoeba. In addition, we have also included useful infographics to help you learn better. Also, our subject experts have answered all written questions following this Class 7 Science chapter on nutrition in different types of animals. Have fun learning!!

Download NCERT Science Class 7 Science Chapter 2 Important Questions and Answers PDF

Introduction to NCERT Class 7 Science Chapter 2: Nutrition in Animals

Animals get their food or nutrition from direct or indirect products of plants and animals. Their nutrition is a summation of their nutritional needs, mode of food intake, and its usage in their bodies. In an animal body, food components such as carbohydrates, proteins, or fats are complex substances that cannot be used in their original form. Thus, these are broken down into simpler substances. This process of breaking down complex substances into simpler ones is known as Digestion. 

Source: Magnet Brains

Now, let us explore different dimensions of digestion in human beings, grass-eating animals, and amoeba. To start learning about the digestive system in these animals, let us first learn about different ways of food intake in different animals.

Different Ways of Taking Food

In the NCERT Class 7 Science Chapter 2, we will learn that each animal type has a distinct way of taking food. Here are the different ways. 

Animals/BirdsWays of Taking Food
Humming BirdUse their Beak to Suck the nectar of flowers 
BeesUse their tongue to Suck the nectar of flowers
SnakesUse their tongue to Swallow their prey
Aquatic animalsUse their mouth to filter small food particles in water
Human BeingsUse tongue to Swallow solid food, either plant or animal product

Digestion in Human Beings

Human Beings consume food through the mouth. After that, the food passes through a continuous canal that is classified into the following compartments:

  • Buccal Cavity
  • Foodpipe or Oesophagus
  • Stomach
  • Small Intestine
  • Large Insteine
  • Anus

All these parts are collectively known as the “Digestive Tract” or the “Alimentary Canal”. The inner walls of important parts of this canal such as the stomach and small intestine are associated with other body parts like the salivary glands, liver, and pancreas that secret digestive juices. Thereafter, these juices break down complex substances into simpler ones. The alimentary canal and associated glands and organs form the “Digestive System” in human beings.

Digestive System: Chapter 2 Nutrition in Animals
Credit: Healthdirect

Mouth and Buccal Cavity

The Buccal Cavity comprises the teeth, tongue, and salivary glands. Let us learn more about that and what happens to the food when it passes through this part of the digestive system:

  • Human beings intake food through the mouth. This process of consuming food is known as “Ingestion”.
  • Thereafter, humans chew food with their teeth. The teeth break down solid food into small pieces mechanically. 
  • Each tooth in the human mouth is rooted in an individual socket. These sockets are known as “Gums”.
  • There are 4 types of teeth in a human being’s mouth- Incisor, Canine, Premolar, and Molar. Each set of teeth has a distinct function. 
  • Milk Teeth: The initial set of teeth in a human being is known as milk teeth. These develop in infancy and typically begin to shed around the ages of six to eight years.
  • Permanent Teeth: The second set of teeth that replaces them is known as permanent teeth. These permanent teeth can endure for a lifetime or may be lost in old age or due to certain dental conditions.
  • Furthermore, the Salivary Glands produce saliva that breaks down the starch into sugar. 
  • Thereafter, the tongue mixes saliva with the food during chewing. Also, it helps human beings swallow food. In addition, it also enables humans to taste food due to the presence of taste buds on the tongue.
Mouth and Buccal Cavity
Credit: Embibe

Foodpipe or Oesophagus 

In this section of NCERT Class 7 Science Chapter 2 notes, we will learn about what happens to food after human beings swallow it.

  • The swallowed food travels through the esophagus or food pipe, which runs along the neck and the chest. It ends in the stomach. Thus, it is the canal through which food reaches from the buccal cavity to the stomach. 
  • Food in the esophagus reaches the stomach with the help of the movements of the wall of the food. 
Food Pipe or Esophagus
Credit: Laparoscopic Surgen Mumbai

Stomach

The stomach is a muscular, thick-walled organ with a flattened J-like shape. It constitutes the widest section of the digestive tract. It receives food from the esophagus at one end and connects to the small intestine at the opposite end. 

Now, let us explore the journey of food in the stomach:

The inner lining of the stomach produces mucus, hydrochloric acid, and digestive enzymes. 

  • The mucus serves as a protective barrier for the stomach lining. 
  • Whereas, hydrochloric acid has the dual role of eliminating bacteria that may accompany the ingested food and creating an acidic environment that facilitates the action of digestive enzymes. 
  • These digestive enzymes are responsible for breaking down proteins into simpler compounds.
  • The entire journey of food in the stomach is known as “Digestion”
Stomach: Nutrition in Animals
Credit: Star Health Insurance

Small Intestine, Liver, and Pancreas

Herein, we will first learn about the different parts and go on to learn about the absorption of food in the small intestine. 

  • Small intestine: It is an extremely coiled part of the alimentary canal. It extends approximately 7.5 meters in length. It receives secretions from both the liver and the pancreas. Additionally, the intestinal wall itself also produces digestive juices.
  • Liver: The liver is a reddish-brown organ located in the upper right part of the abdomen, and it is the largest gland in the human body. It produces bile, which is stored in the “Gall Bladder”. Bile plays a crucial role in the digestion of fats.
  • Pancreas: The pancreas is a sizable, cream-colored gland positioned just below the stomach. Pancreatic juice is responsible for breaking down carbohydrates, fats, and proteins into simpler compounds.

Absorption of Food in Small Intestine

Partly digested food from the stomach reaches the lower part of the small intestine. In this part, the food mixes with intestinal juices. After mixing with the juices, all components of the food are broken down. Herein, proteins break into amino acids; carbohydrates into glucose; and fats into glycerol and fatty acids. 

  • In the small intestine, the digested food travels into the blood vessels present in the intestinal wall. This process is known as “Absorption”. 
  • These intestinal walls contain numerous finger-like outgrowth, known as “Villi”. They enhance the surface area available for the absorption of digested food. Within each villus, there is a network of fine and small blood vessels situated close to the surface. The surface of the villi absorbs the digested nutrients. These absorbed substances are then conveyed through the blood vessels to various organs, where they are used to construct complex compounds, such as the proteins essential for bodily functions. This process is referred to as “Assimilation”.
Three Parts of Small Intestine: Nutrition in Animals
Credit: Pinterest

Large Intestine

The large intestine is broader and more compact than the small intestine. It is around 1.5 meters in length. 

  • Its primary role is to extract water and certain salts from undigested food substances.
  • The remaining waste moves into the rectum and stays there, forming semi-solid feces. Periodically, this fecal material is eliminated through the anus, a process known as “Egestion”.
Large Intestine: Nutrition in Animals
Credit: Canadian Cancer Society

Digestion in Grass-Eating Animals

Here is how the digestive system of grass-eating animals works:

  • Grass-eating animals like cows, goats, and buffalos swiftly swallow food and store it in a part of their stomach called “Rumen”. In this part of the stomach, the food is partially digested. At this stage, the food is known as “Cud”. 
  • After some time, cud comes back into its mouth in small lumps. The animal chews it again. This special process is known as “Rumination”. The animals that do this are called “Ruminants.”

As grass contains a carbohydrate called cellulose, ruminants like cattle and deer have bacteria in their rumen that help them break down cellulose during digestion. However, many animals, including humans, are unable to digest cellulose.

Feeding and Digestion in Amoeba

In this part of the NCERT Class 7 Science Chapter 2, we learn about the digestive system of an unicellular organism- Amoeba. 

What is Amoeba?

An amoeba is a tiny, one-celled creature that lives in pond water. It has a protective outer layer, a round, dense centre, and lots of small bubble-like pockets inside its body. Amoeba is always changing its shape and where it is. To move around and catch its food, it sticks out finger-like projections called pseudopodia or “false feet.”

Feeding and Digestion in Amoeba

  • Amoeba eats microorganisms. When it detects food, it extends its pseudopodia around the food and wraps it up. The food gets enclosed in a special space called a “Food Vacuole.”
  • Thereafter, amoeba releases digestive juices into the food vacuole. These juices work on the food, breaking it into simpler parts. Over time, the amoeba absorbs these digested nutrients.
  • The substances that Amoeba absorbs are used for growing, staying healthy, and making more amoeba. Anything that the Amoeba can’t digest is pushed out of its body by the vacuole.

Other Important Topics in NCERT Class 7 Science Chapter 2: Nutrition in Animals

Tooth Decay

Bacteria are typically present in our mouths without posing harm. Nevertheless, failing to maintain oral hygiene by not cleaning our teeth and mouth after eating allows harmful bacteria to proliferate. These harmful bacteria metabolize sugars from leftover food. This produces acids. Over time, these acids progressively erode the teeth, a condition known as tooth decay.

Diarrhea

At times, you might have encountered the urge to have frequent, watery bowel movements. This condition is referred to as “Diarrhoea”. 

  • It can be triggered by an infection, consuming contaminated food, or difficulty in digesting food. 
  • It is quite common in India, especially among children.

Oral Rehydration Solution (ORS)

In severe cases, diarrhea can become life-threatening due to the significant loss of water and essential salts from the body. Therefore, we must not ignore diarrhea. Even before seeing a doctor, it is important to provide the patient with plenty of boiled and cooled water containing a pinch of salt and sugar, which is called an “Oral Rehydration Solution (ORS)”. This helps in replenishing lost fluids and electrolytes.

NCERT Solutions Class 7 Science Chapter 2: Nutrition in Animals

Now, let us learn answers to questions in NCERT Class 7 Science Chapter 2: Nutrition in Animals. 

Ques 1. Fill in the blanks

a. The main steps of nutrition in humans are_(1)____________, _(2)______________, _(3)____________, __(4)___________, and __(5)______________.

b. The largest gland in the human body is_________________.

c. The stomach releases hydrochloric acid and_____________ juices which act on food.

d. The inner wall of the small intestine has many finger-like outgrowths called___________.

e. Amoeba digests its food in the___________.

Ans:

a. (1) Ingestion; (2) Digestion; (3) Absorption; (4) Assimilation; (5) Egestion

b. Liver

c. Digestive

d. Villi

e. Vacuole

Ques 2. Which of the following statements are True or False:

a. Digestion of starch starts in the stomach. 

b. The tongue helps in mixing food with saliva. 

c. The gall bladder temporarily stores bile.

d. The ruminants bring back swallowed grass into their mouth and chew it for some time.

Ans:

a. False

b. True

c. True

d. True

Ques 3. Which of the following options is correct?

a. Fat is completely digested in the

   (i) Stomach

   (ii) Mouth

   (iii) Small Intestine
  (iv) Large Intestine

b. Water from the undigested food is absorbed mainly in the

    (i) Stomach

    (ii) Food Pipe

    (iii) Small Intestine

    (iv) Large Intestine

Ans:

a. (iii) Small Intestine

b. (iv) Large Intestine

Ques 4. Match the following items in Column I with that in Column II

Column I- Food ComponentsColumn II- Product(s) of Digestion
CarbohydratesFatty acids and Glycerol
ProteinsSugar
FatsAmino acids

Ans:

Column I- Food ComponentsColumn II- Product(s) of Digestion
CarbohydratesSugar
ProteinsAmino acids
FatsFatty acids and Glycerol

Ques 5. What are villi? What is their location and function?

Ans: Villi refers to finger-like outgrowth or projections. They are found in the intestinal walls of the small intestine. Within each villus, there is a network of fine and small blood vessels situated close to the surface of the intestine.

They enhance the surface area available for the absorption of digested food. The surface of the villi absorbs the digested nutrients. These absorbed substances are then conveyed through the blood vessels to various organs.

Ques 6. Where is the bile produced? Which component of the food does it help to digest?

Ans: The liver produces bile juice. 

Bile helps to digest food. It breaks down large fat globules into smaller ones.

Ques 7. Name the type of carbohydrate that can be digested by ruminants but not by humans. Give the reason also.

Ans: Cellulose.

It can be digested by ruminants but not by human beings because humans do not produce the cellulase enzyme needed to digest the cellulose.

Ques 8. Why do we get instant energy from glucose?

Ans: Glucose is a basic form of sugar that quickly enters the bloodstream. In contrast, other carbohydrates need to be converted into glucose before they can be absorbed. Because glucose is readily absorbed, it provides a quick source of energy.

Ques 9. Which part of the digestive canal is involved in:

a. Absorption of food___________________.

b. Chewing of food_________________.

c. Killing of bacteria______________.

d. Complete digestion of food____________.

e. Formation of faeces______________.

Ans:

  • Small intestine
  • Buccal cavity
  • Stomach
  • Small intestine
  • Large intestine

Ques 10. Write one similarity and one difference between the nutrition of amoeba and human beings.

Ans:

  • The similarity between amoeba and human beings’ nutrition:  Both practice holozoic nutrition.
  • Difference between human and amoeba digestion: Humans consume food through the buccal cavity, while in amoeba, food is taken in through pseudopodia.

Ques 11. Match the items in Column I with suitable items in Column II

Column IColumn II
a. Salivary gland(i) Bile juice secretion
b. Stomach(ii) Storage of undigested food
c. Liver(iii) Saliva secretion
d. Rectum(iv) Acid release
e. Small intestine(v) Digestion is completed
f. Large intestine(vi) Absorption of water
(vii) Release of faeces

Ans:

Column IColumn II
a. Salivary gland(iii) Saliva secretion
b. Stomach(iv) Acid release
c. Liver(i) Bile juice secretion
d. Rectum(ii) Storage of undigested food
e. Small intestine(v) Digestion is completed
f. Large intestine(vi) Absorption of water

Ques 13. Can we survive only on raw, leafy vegetables/grass? Discuss.

Ans: We cannot survive solely on raw, leafy vegetables because they primarily contain cellulose, which our bodies cannot digest due to the absence of cellulose-digesting enzymes. We require other sources of nutrition for a balanced diet.

Also Read:

NCERT Class 7 Science Chapter 1 Nutrition in Plants: Notes, Solutions, Free PDF

FAQs

Q.1. What are the different parts of the digestive tract?

Ans: It comprises the mouth, buccal cavity, stomach, liver, pancreas, small intestine, large intestine, and anus.

Q.2. What is the other name for the digestive tract?

Ans: It is also known as the Alimentary Canal.

Q.3. What are milk teeth and permanent teeth?

Ans: Milk Teeth: The initial set of teeth in a human being is known as milk teeth. These develop in infancy and typically begin to shed around the ages of six to eight years.

Permanent Teeth: The second set of teeth that replaces them is known as permanent teeth. These permanent teeth can endure for a lifetime or may be lost in old age or due to certain dental conditions.

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